As a small-sized camera system, there has been used an imaging apparatus having a camera control unit and a camera head separate from the camera control unit, the camera head being employed with an imaging device such as a charge coupled device (CCD).
The imaging apparatus having such separate camera head is provided with the camera head (also simply referred to as a camera head) and a camera control unit (CCU). The camera head outputs a pixel signal (image signal) obtained by an image pickup device such as a charge coupled device (CCD). The CCU has a signal processing circuit for obtaining a video signal to display an image based on the pixel signal output from the camera head. The camera head and the CCU are connected to each other by a dedicated camera cable.
The imaging apparatus outputs the video signal from the CCU to a display device so that an image of a subject captured by the camera head can be observed on a screen of the display device.
An example of a conventional imaging apparatus having a separate camera head is disclosed in JP-A-11-341337. The imaging apparatus disclosed in this publication is designed to correct a phase difference generated between a first synchronizing signal for driving the camera head and a second synchronizing signal for setting timing of the signal processing circuit due to the length of the camera cable to thereby correct a delay time caused by the cable length.
The conventional imaging apparatus having the separate camera head is configured to have the camera cable having a given length for connecting the camera head and the CCU.
However, the length of the camera cable slightly varies due to a manufacturing margin even when the length is designed to be the given length.
When the ratio of the variation to the length of the cable is constant, the individual variation of the cable length increases as the length of the camera cable is designed to be longer. The time required for signal transmission becomes longer as the length of the camera cable increases. Accordingly, when the camera cable is long, the variation of the signal delay time caused by the individual variation of the cable length becomes larger.
Moreover, when the band of the signal used in the imaging apparatus is widened and the resolution or frame rate becomes higher, the requirement to reduce the variation of the signal delay time becomes severe. It is therefore necessary to improve various specifications of the camera cable to a higher level to reduce the variation range of the delay time.
There is however a limit to improve specifications of the camera cable with respect to the variation of the delay time. It is therefore preferable that the imaging apparatus can suitably perform signal processing in accordance with the delay time of the camera cable to keep desired performance.